1. Field of the Invention
This invention relates to an integrated circuit and particularly to an integrated circuit that realizes higher speed, more advanced functions and reduction in the number of elements.
2. Description of the Related Art
The Si semiconductor integration technique has achieved satisfactory improvement in the degree of integration and speed from 2 μm to 1 μm, 0.5 μm, 0.25 μm, 0.13 μm and 0.09 μm. Moreover, some semiconductor manufacturers plan to achieve 0.065 μm. Also the exposure technique has progressed from g-line to i-line exposure to phase shift exposure and further to an excimer light source. Currently, an excimer light source plus phase shift exposure is employed.
A concave mirror technique that enables construction of a miniature optical system, which was difficult to realize in the X-ray contraction projection technique, is being completed, and realization of an X-ray stepper/X-ray scanning exposure system that achieves the order of 0.01 μm can be expected. The semiconductor processing technique is now reaching the level of 10 nm.
Semiconductor circuit elements have been miniaturized in accordance with the K-factor (scaling factor) rule. The technique that led the miniaturization overcame engineering problems and dimensions (processing accuracy, processing method, establishment of techniques for eliminating various contaminant defects control of chemical reactions and the like) rather than problems of physical principles (semiconductor operation principle and the like), and did not need change of physical concepts themselves (scaling rule, semiconductor band theory, transistor operation principle and the like).
FIG. 1 is a structural block diagram showing an example of a conventional high-speed A/D converter (flash-type) formed on one chip. In FIG. 1, a voltage inputted to a ladder resistor (series resistor network) 30 is inputted to an encoder 32 via a comparator 31, then converted to a digital signal and outputted. 33 represents a reference power source for the comparator 31.
In such a high-speed A/D converter, 2n-1 units of comparators and resistors are necessary for A/D conversion of N bits. That is, an extremely large number of elements are required.
However, as the progress of the X-ray exposure technique and the electron beam exposure technique has enabled ultrafine processing of 0.065 μm or less, the influence of a tunnel effect, which is a physical phenomenon, causes increase in leakage current, injection of hot electrons, avalanche breakdown and the like occur in a MOS oxide film, which is a conventionally used insulating material. Therefore, the conventional scaling factor cannot suffice and a problem arises that the operation becomes unstable in an LSI.
Although a one-electron transistor or the like is proposed as an ultimate element, it requires a cryogenic environment and its one-electron quantum effect makes the operation unstable under the law of quantum-mechanical establishment. In order to actively utilize the quantum effect, introduction of the quantum effect such as resonant tunneling by using a compound such as SiGe—SiC is researched. To aggregate the functions of an LSI, it is necessary to introduce a quantum interference effect and thus realize advanced logical functions. However, there is a problem that it is extremely difficult to generate quantum interference in a solid substance at a room temperature because of the influence of various scattering effects (impurity scattering, phonon scattering and the like).
A prior art of forming a fine vacuum tube on a substrate is disclosed in JP-A-7-193052.